Find the magnetic field at P and P' on the axis of a circular coil of radius a = 18.7 cm (see figure below). T

Find the magnetic field at P and P' on the axis of a circular coil of radius a = 18.7 cm (see figure below). The coil consists of 10 turns of wire carrying a current of 3.67 A in the direction indicated. (Hint: the magnetic field on the axis of a coil with N turns is N times the magnetic field from a single loop.)

http://www.webassign.net/colfunphys1/21-p-033-alt.gif

B(induced by coil) = 2e-7(m/r^3)
m = NIA
m = (10)(3.67)(.110) = 4.0318

r = sqrt(a^2 + z^2) where a is the radius and z is the distance from the center of the coil
r = sqrt(.187^2 + .30^2) = .354

B = 2e-7(4.0318/.354^3) = 1.82e-5 T

P and P' are the same and = 1.82e-5 T